So we have to go
back to the first material when I wrote RENDER IT. For the next
thing we will work with this older values. Hopefully you make a
copy of it ;). If not it would be a good idea to make the
material again. Anyway, if you are done create a new light source
and use the position parameters as well as the light parameters
as shown below.

When done just
render the scene again. If you still can, play around with
position, color and so on. ;)